Structural Dimension Effects of Plasma Hydrogenation on Low-Temperature Poly-Si Thin Film Transistors

Abstract

The effects of plasma hydrogenation on various N- and P-channel polycrystalline-silicon (poly-Si) thin film transistors (TFT's) fabricated at a maximum temperature of 600° C were analyzed systematically. Device characteristics, such as threshold voltage and field-effect mobility, were improved significantly with hydrogenation time as the channel length of poly-Si TFT's was decreased from 20 µm and 2.5 µm. However, hydrogenation effects on the characteristics of poly-Si TFT's, of which channel width was varied from 2.5 µm to 20 µm, were almost identical. In thin active layer (50 nm) TFT's, the device performance was improved significantly compared with thick (100 nm and 150 nm) devices with hydrogenation time while the thickness of gate poly-Si may not be directly related with hydrogenation effects, probably due to the fact that the hydrogen atoms may diffuse along the channel region while the diffusion of hydrogen atoms through gate poly-Si may be negligible.